1. Technical Field
The present disclosure relates generally to a portal apparatus employing a seal for maintaining a fluid-tight connection with a surgical instrument. In particular, the disclosure relates to a portal apparatus employing a seal adapted to expediently deform upon insertion of the instrument.
2. Background of Related Art
Surgical procedures such as laparoscopic, arthroscopic, and endoscopic procedures in general are termed minimally invasive at least in part because the incision required is relatively small, perhaps one inch in length or less. Small incisions are preferred because they are inherently less traumatic to the body tissue. Also, small incisions only subject internal organs to a minimum of exposure to the contaminants in the outside atmosphere. Thus, small incisions enable shorter hospital stays and faster recoveries with less pain and scarring than is common with the larger incisions required for conventional surgery.
Endoscopic surgery is possible due in part to the availability of instruments designed specifically for this purpose. A cannula, for example, is an elongated tube, typically 5 mm to 13 mm in diameter, which may be configured to have a distal end inserted through the small incision to provide a working conduit to an internal body cavity adjacent an operative site. The body cavity is often inflated with an insufflation gas, carbon dioxide for example, to separate the body wall from vital organs. This provides a space where a surgeon may introduce viewing equipment or maneuver tools into position without damaging surrounding tissue. Various other instruments may then be inserted and withdrawn through the cannula for access to the working space and operative site. In order to fit through a cannula and also to enable a surgeon to manipulate tissue far removed from the incision, instruments adapted for endoscopic surgery typically include a long and narrow cylindrical shaft. A tool on the distal end of the shaft may be inserted through the cannula and positioned within the body near the operative site, while a working head at the proximal end of the shaft remains in the outside environment to be handled by a surgeon to control the tool.
Endoscopic procedures generally require that any instrumentation inserted into the patient's body be sealed, i.e. provisions must be made to ensure insufflation gasses, blood and other fluids do not escape the body through the cannula. Furthermore, a seal acts to prevent contamination of the body cavity by the outside environment. In the absence of such a fluid-tight seal, many of the attendant advantages of minimally invasive surgery are lost. Cannulas are often provided with a washer-shaped ring of a flexible material, such as an elastomer, sized so as to accommodate the cylindrical shaft of a surgical instrument. An orifice through the seal material can be sized just smaller than the instrument to be inserted so that a central portion of the seal material is displaced by the instrument and maintains contact with the shaft. The quality of the seal created depends in part on the amount of seal material contacting the shaft. Leakage of air and insufflation gasses might occur if the amount of contacting material is insufficient. Accordingly, a need exists for a cannula with a seal capable of providing a robust engagement with an instrument.